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Non‐Kekulé quinoidal azaacences m‐A (1 a,b) were synthesized and compared to their para‐ and ortho‐quinodimethane analogues. m‐A display high diradical characters (1 b: y0 = 0.88) due to their meta‐quinodimethane (m‐QDM) topology. Electron paramagnetic, nuclear magnetic resonance spectroscopies and supraquantum interference device measurements in combination with quantum‐chemical calculations revealed singlet ground states for m‐A with singlet‐triplet gaps ΔEST (0.13–0.25 kcal mol−1) and thermally populated triplet states. These non‐Kekulé structures are over all void of zwitterionic character and possess record high two‐photon absorption cross sections over a broad spectral range in the near‐infrared. [ABSTRACT FROM AUTHOR]

Ionic discotic liquid crystals combine ion conduction with fluid, yet ordered, liquid crystal phases at ambient temperature, making them suitable nanomaterials for ion transport and energy storage. A series of Janus-type hexa-peri-hexabenzocoronenes (HBCs) with ionic (sulfonate) groups covalently bonded to the HBC core, and tetraalkylammonium counterions (sizes from 0.15 to 0.95 nm) are synthesized and investigated with respect to the self-assembly and ion dynamics. We find that the counterion size affects the nanoscale self-assembly and ionic conductivity in opposite ways. Smaller counterions act as structure formers, whereas larger ones act as structure breakers. The latter exhibits the highest ion dc-conductivity. We quantify the effect of Coulomb interactions on the self-assembly, the glass temperature Tg (which was found to vary by 30 K), and the dc-conductivity (varying by 4 orders of magnitude). The precise synthesis of tailor-made ionic discotic liquid crystals with the HBC core and the characterization of their physical properties revealed that ion-conduction and nanoscale self-assembly in HBCs can be modulated by tuning electrostatic interactions, e.g., by adjusting the size of counterions. [ABSTRACT FROM AUTHOR]

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We report soluble tetrakis‐biphenylyl substituted pentacenes comprised of sp2 carbons and synthesized from pentacene‐5,7,12,14‐tetraone. Intramolecular Yamamoto coupling of two tetrakis(chlorobiphenylyl)pentacenes yields helical, doubly wrapped pentacenes, in which the quaterphenylene units solubilize the pentacenes and shield their central anthracene units to an unprecedented degree. The criss‐cross‐bridged pentacenes resist (photo)oxidation, Diels–Alder reactions and are much less reactive than TIPS‐ethynylated pentacene. Extension of this concept might provide access to the larger acenes. [ABSTRACT FROM AUTHOR]

The solvent and catalyst free thermolysis of biphenylenes at 350 °C furnishes [n]cyclo‐ortho‐phenylenes ([n]COPs, n=4–10) in one step and in high yields. At 400 °C biphenylene dimerizes into tetraphenylene, but lower reaction temperatures produce cyclooligomers. If suitably substituted, the oligomers are soluble and can be isolated and characterized. The products are exclusively cyclic. In the crystalline state, [6]COP displays an alternating crown‐shaped conformation. [ABSTRACT FROM AUTHOR]

The photooxidative stability of a series of doubly bridged anthracenes was evaluated after their preparation via twofold macrocyclization of a bis(resorcinyl)anthracene. Lightfastness correlates with the energy levels of the highest occupied molecular orbital (HOMO), resulting in superior stability of the tetraesters compared to the tetraethers. The lengths and steric demand of the linker only plays a minor role for the ester‐based compounds, which can be prepared in reasonable yields and thus tested in proof‐of‐concept organic light‐emitting diodes. Double ester‐bridging allows deep blue electro‐luminescence, highlighting the importance of the choice of the functional groups used for macrocyclization. [ABSTRACT FROM AUTHOR]

Triisopropylsilyl‐(TIPS)‐alkynylated phenazinothiadiazoles were prepared by the condensation of halogenated ortho‐quinones and TIPS‐alkynylated 5,6‐diamino‐2,1,3‐benzothiadiazole with different combinations of halogen substituents. The compounds pack in brickwall motif of head‐to‐head dimers featuring intermolecular S−N contacts and short π‐π distances, suggesting their suitability as n‐channel materials in organic thin film transistors. The halogenated phenazinothiadiazoles show electron mobilities μmax ranging between 0.14 cm2 V−1 s−1 and 0.76 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Four substituted nonacenes were prepared and characterized by UV‐vis and EPR spectroscopy and X‐ray crystallography. The compounds are the most stable and soluble nonacenes to date – due to six strategically placed triisopropylsilyl(TIPS)‐ethynyl groups. They are stable for several weeks in the solid state. In dilute solution their half‐life is 5–9 h. Crystal structure analyses of two nonacenes prove their structures. A nonacene derivative was tested in a solution‐processed transistor and exhibits ambipolar charge transport (μe=0.007 cm2/Vs; μh=0.023 cm2/Vs). [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two series of regioisomeric dicyanomethylene substituted dithienodiazatetracenes with formal para‐ or ortho‐quinodimethane subunits were synthesized and characterized. Whereas the para‐isomers (p‐n, diradical index y0=0.01) are stable and isolable, the ortho‐isomer (y0=0.98) dimerizes into a covalent azaacene cage. Four elongated σ‐CC bonds are formed and the former triisopropylsilyl(TIPS) ‐ethynylene groups transformed into cumulene units. The azaacene cage dimer (o‐1)2 was characterized by X‐ray single crystal structure analysis and temperature‐dependent infrared (IR), electron paramagnetic resonance (EPR, solid‐state), nuclear magnetic resonance (NMR) and ultraviolet‐visible (UV/Vis) spectroscopies (solution) indicating reformation of o‐1. [ABSTRACT FROM AUTHOR]

We present the synthesis of two sets of spiro‐connected azaacene dimers. Their geometry and electronic coupling are critically determined by a secondary linker, i. e. an etheno‐ and an ethano‐bridge. The core fragment of the etheno‐bridged dimer corresponds to a conformationally locked cis‐stilbene. Optoelectronic properties, single crystal X‐ray structures and stability with respect to oxidation of the conjugated and non‐conjugated dimers are reported and compared. The conjugated dimers exhibit smaller optical gaps and bathochromically shifted absorption maxima, but are prone to unexpected oxygen addition, dearomatizing one of the azaacene substituents. [ABSTRACT FROM AUTHOR]

We report the synthesis and optoelectronic properties of 16 thiophene‐based heterophenoquinones. These compounds were accessed in a convergent and modular approach, allowing for their efficient synthesis. Tuning of the optical band gap was achieved through π‐extension by annulation of a benzene or tropone moiety to the thiophene, oxidation, change of the heteroatom or by attachment of a donor substituent to the thiophene core. The resulting compounds display intense colors covering the entire visible spectrum. We identified structure‐property relationships and their impact on the HOMO and LUMO levels. Additionally, these materials change color upon reduction and according to in situ ultraviolet‐visible‐near infrared (UV‐vis‐NIR) and electron paramagnetic resonance (EPR) spectro‐electrochemistry, they are promising electrochromes with cathodic color changes. Seven different electrochromic devices were constructed which all displayed a change in color upon reduction, demonstrating the potential of these new dyes in for example tintable glass. [ABSTRACT FROM AUTHOR]

This work presents the 2nd generation of cata‐annulated azaacene bisimides with increased electron affinities (up to −4.38 eV) compared to their consaguine conventional azaacenes. These compounds were synthesized via Buchwald–Hartwig coupling followed by oxidation with MnO2. Crystal structure engineering through variation of the bisimide substituents furnished crystalline derivatives suitable for proof of concept organic field effect transistors with electron mobilities up to 2.2×10−4 cm2(Vs)−1. Moreover, we were able to characterize the charge carrying species, the radical anion, using electron paramagnetic resonance and absorption measurements. [ABSTRACT FROM AUTHOR]

A strongly twisted benzo‐fused tris‐cycloheptenylene, containing three dibenzosuberenone units fused to a common benzene ring, was subjected to Ramirez olefination and subsequent palladium‐catalyzed Suzuki‐Miyaura cross‐coupling with 4‐substituted phenylboronic acids. The high steric demand within the overcrowded, benzene‐rich benzo‐fused tris‐cycloheptenylenes enforced an unprecedented 1,2‐rearrangement upon π‐extension during the Suzuki coupling reaction. According to crystal structure analysis, the resulting negatively curved polycyclic aromatic hydrocarbons consist of two heptagons and one octagon surrounding a central benzene ring as a result of strain release. In the solid state, the materials exhibit a blue to blue‐green fluorescence with increased quantum yields and a hypsochromic shift of the emission maxima compared to their respective solutions. [ABSTRACT FROM AUTHOR]

An oxidation reaction of hydroxyhomosumanene on silica gel providing homosumanene ortho‐quinone and its synthetic application for azaacene‐fused homosumanenes is described. Hydroxyhomosumanene is photochemically oxidized by air, when it is coated on silica gel; this aerobic oxidation proceeds faster than that of planar analogues. The difference of such reactivity was attributed to the unusual keto‐enol tautomerization due to structural difference between planar and curved π‐system. The homosumanene ortho‐quinone was used in the synthesis of several azaacene‐fused homosumanenes, azaacenohomosumanenes. X‐ray diffraction analysis of the single crystals revealed their columnar stacking structures due to the interactions between each bowl. Azaacenohomosumanenes exhibited high electron affinity due to the combination of buckybowl and electron‐deficient azaacene moieties. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cyclopentannulation was explored as a strategy to access large, stable azaarenes. Buchwald–Hartwig coupling of previously reported di‐ and tetrabrominated cyclopentannulated N,N′‐dihydrotetraazapentacenes furnished stable azaarenes with up to 13 six‐membered rings in a row and a length of 3.1 nm. Their optoelectronic and semi‐conducting properties as well as their aromaticity were investigated. [ABSTRACT FROM AUTHOR]

Tetraiodotetraazapentacene I4TAP, the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS‐ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air‐stable monoanion and relatively air‐stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non‐halogenated TAP and Br4TAP. I4TAP is an n‐channel material in thin‐film transistors with average electron mobilities exceeding 1 cm2 (Vs)−1. [ABSTRACT FROM AUTHOR]

Four N‐acenoacenes were synthesized and analyzed for their optoelectronic properties and solid‐state packings. Two of the regioisomeric acridinoacridines are TIPS‐ethynylated, whereas the other pair are Boc‐ and triflate substituted derivatives. The two TIPS‐ethynyldiazaacenoacenes were processed into organic thin‐film transistors with saturation hole mobilities reaching 2.9×10−2 cm2(Vs)−1. [ABSTRACT FROM AUTHOR]

Brominated pentannulated dihydrotetraazapentacenes were prepared by gold‐ or palladium‐catalyzed 5‐endo‐dig cyclization of TIPS‐ethynylated dihydrotetraazaacenes (TIPS = triisopropylsilyl). Post‐functionalization was demonstrated by Sonogashira alkynylation and Rosenmund‐von Braun cyanation. Calculations predict these species to act as n‐type semiconductors, which was verified for two derivates through characterization in organic field‐effect transistors. [ABSTRACT FROM AUTHOR]

Buchwald‐Hartwig coupling of a triisopropylsilyl (TIPS)‐ethynylated dibromo‐N,N'‐dihydrotetraazapentacene with 1,4‐bis(TIPS‐ethynyl)‐2,3‐diaminonaphthalene furnishes a dihydrohexaazaoctacene. Its oxidation with MnO2 results in a 7,7'‐bi(hexaazaoctacenyl). In addition to eight TIPS‐ethynyl groups, the bioctacene motif protects the azaoctacene subunits. The biazaoctacenyl displays a τ1/2 of > 5 d in dilute solution under ambient conditions. In the crystalline state it is persistent for > 10 months. [ABSTRACT FROM AUTHOR]

We describe the on‐surface dehalogenative homocoupling of benzylic bromides, namely bis‐bromomethyl‐ and bis‐gem‐(dibromomethyl) naphthalene as a potential route to either hydrocarbon dimers or conjugated polymers on Au(111). While bis‐gem‐(dibromomethyl) naphthalene affords different dimers with naphthocyclobutadiene as the key intermediate, bis‐bromomethyl naphthalene furnishes a poly(o‐naphthylene vinylidene) as a non‐conjugated polymer which undergoes dehydrogenation toward its conjugated derivative poly(o‐naphthylene vinylene) upon mild annealing. A combination of scanning tunneling microscopy, non‐contact atomic force microscopy and density functional theory calculations provides deep insights into the prevailing mechanisms. [ABSTRACT FROM AUTHOR]

Sixfold TIPS‐ethynylation combined with fourfold bromination of the armchair edges furnishes a long‐lived, soluble heptacene; π‐extension via Stille coupling accesses a persistent tetrabenzononacene. Both types of acenes were stabilized best by double TIPS‐ethynylation on every other benzene ring. Tetrabromoheptacene is an ambipolar transistor material (up to 0.036 cm2 V−1 s−1 n‐channel), which was corroborated by generation of its monoanion and monocation. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An increasing number of organic light‐emitting diodes (OLEDs) is nowadays based on the use of polymers as the emissive material. For this material class in particular, solution‐processing of the OLEDs has gained traction in both research and industry. However, in order to access multilayer material systems, orthogonal solvents must be used to prevent dissolution of previously prepared layers. The use of crosslinkers can facilitate this production method by reducing the number of orthogonal solvents needed since insoluble networks are generated. In this work, a novel bisazide crosslinker is employed to insolubilize Super Yellow, a polyphenylene‐vinylene emitter. This allows the use of an additional poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine electron blocking layer (EBL) from the same solvent. Devices including the blocking layer show improved efficacies compared to reference devices without the additional EBL, while also maintaining the emission spectrum. Using the upscalable technique of doctor blading, OLEDs were fabricated which showed a particularly noticeable effect of the blocking layer with a nearly twofold increase in luminance and a 56% increase in current efficacy. [ABSTRACT FROM AUTHOR]

Abstract Background Several features are known to correlate with the GC-content in the human genome, including recombination rate, gene density and distance to telomere. However, by testing for pairwise correlation only, it is impossible to distinguish direct associations from indirect ones and to distinguish between causes and effects. Results We use partial correlations to construct partially directed graphs for the following four variables: GC-content, recombination rate, exon density and distance-to-telomere. Recombination rate and exon density are unconditionally uncorrelated, but become inversely correlated by conditioning on GC-content. This pattern indicates a model where recombination rate and exon density are two independent causes of GC-content variation. Conclusion Causal inference and graphical models are useful methods to understand genome evolution and the mechanisms of isochore evolution in the human genome.